Dear Dietitian:

I seem to get three or four bladder infections every year. My friend told me to try cranberry supplements. Do they work?

Meredith

Dear Meredith,

Anyone who has suffered through a urinary tract infection (UTI) knows the discomfort that comes with it. As many as six million people endure a UTI each year; most are healthy females ages 20 to 40. A UTI occurs when bacteria, such as Escherichia coli (E. Coli), make their way to any part of the urinary system- the bladder, kidneys, ureters, and urethra. 

Some prefer a more natural approach to healing and may choose cranberry juice or tablets to defend against UTIs. Cranberries were once thought to help UTIs by making the urine more acidic, making it more difficult for bacteria to survive. More recent research has found that cranberries contain a nutrient called proanthocyanins (PACs) that change the surface of E. Coli, making it less likely to stick to the urinary tract. 

In an analysis of randomized controlled trials (RCTs), the gold standard of research, Wang et al. found that cranberry-containing products were associated with UTI prevention, particularly for women with recurrent UTIs (1). Several other studies showed similar results. It is important to note that cranberry products do not treat UTIs but aid in their prevention.

Overall, most well-designed studies show that cranberries help prevent recurrent UTIs in healthy middle-aged women. Studies did not produce similar results in elderly populations. 

The question that follows is, “How much cranberry is needed?” The consensus is that 36 mg of PAC equivalents each day is required for UTI prevention. This amount can be found in one to two cups of cranberry juice cocktail (26% cranberry juice) (2). If you choose a supplement or extract form, check the label for PAC equivalents. 

Cranberry products are considered safe, but some have reported stomach upset and diarrhea when using them. Keep in mind that cranberry juice cocktail tends to be high in sugar, although there are lower-sugar versions. Cranberries, extract, and supplement forms are high in oxalates. Oxalates bind with calcium and increase the risk of kidney stones. Do not use cranberry products if you are prone to kidney stones.

When choosing any supplement, select one with USP on the label. The United States Pharmacopeia (USP) is a non-profit organization that tests supplements and medications for quality, potency, and absorbability. USP helps you get the most for your money.

Until next time, be healthy!

Dear Dietitian

Disclaimer: This column is for educational purposes and is not a substitute for medical care. Talk to your healthcare provider if you think you have a urinary tract infection and follow their recommendations.

Citations

1. Wang CH, Fang CC, Chen NC, Liu SS, Yu PH, Wu TY, Chen WT, Lee CC, Chen SC. Cranberry-containing products for prevention of urinary tract infections in susceptible populations. Arch Intern Med 2012;172:988–96.
2. Wight CE, Thornby KA. Evidence to support use of cranberry to prevent and treat UTIs is limited. Pharmacy Today. 2017 Jan 23(1): 29.